The present invention is directed to a method for reducing the percent decomposition of aromatic carbonates in reaction mixtures, and in particular a method for reducing the percent decomposition of aromatic carbonates by the addition of decomposition-reducing additives to mixtures which contain catalyst components.
Aromatic carbonates find utility as monomers in the preparation of polycarbonates. For example, a popular method of polycarbonate preparation is the melt transesterification of aromatic carbonates with bisphenols. Various methods for preparing aromatic carbonates have previously been described in the literature and are utilized by industry. A useful method for the preparation of aromatic carbonates involves the direct carbonylation of aromatic hydroxy compounds with carbon monoxide and oxygen, catalyzed by catalyst compositions typically comprising a metal catalyst, various metal co-catalysts, a salt source, and optionally an organic solvent and base. However, the desired aromatic carbonates produced by the catalytic carbonylation of aromatic hydroxy compounds are typically susceptible to decomposition in the resulting reaction mixtures due to the presence of one or more of the components of the catalyst composition or other reaction byproducts such as, but not limited to, water. Consequently, a long felt, yet unsatisfied need exists for new and improved methods for reducing the percent decomposition of aromatic carbonates in post-carbonylation reaction mixtures, so that the desired aromatic carbonate can be isolated in high yield during post reaction processing.
In one embodiment, the present invention is directed to a method for reducing the percent decomposition of an aromatic carbonate in a first reaction mixture comprising said aromatic carbonate, the method comprising the step of adding at least one decomposition-reducing additive to said first reaction mixture so as to produce a second reaction mixture in which the percent of said aromatic carbonate present in said second reaction mixture after a predetermined amount of time is greater than the percent of said aromatic carbonate that would be present in the first reaction mixture in the absence of adding the decomposition-reducing additive, after the same predetermined amount of time.